Lithium chloride is a high value, potential byproduct of power generation from geothermal brines. Usage of lithium is increasing, and the United States is the major supplier to nonproducing countries. Prior art recovery of lithium from brines involves either complicated and time-consuming extraction methods, principally extraction in alcohol, addition of large amounts of costly reagents to precipitate the lithium, or the use of ion-exchange resins, which limits the volume of brine to be treated at any one time.
For example, U.S. Pat. No. 3,537,813 to Nelli et al. discloses a process for recovering lithium from brines comprising adding a chloride or bromide of a metal selected from a group consisting of ferric iron, cobalt and nickel to liquid brine under acidic conditions, allowing the metal chloride to react with the lithium salts such as lithium chloride, to produce a soluble compound, extracting the soluble compound with water insoluble organic solvents, reextracting the compound from the organic solvent with water, and separating the lithium salt from the metallic chloride or bromide. This method has the disadvantage of requiring addition of large amounts of costly reagents. Also, the lithium chloride, which has been extracted from the organic solvent, must then go through another recovery step to separate it from the metallic chloride or bromide compound.
U.S. Pat. No. 4,159,311 to Lee et al. teaches a process for removing lithium from aqueous brines comprising contacting the brine with an anion exchange resin so that the lithium is adsorbed onto the resin, and eluting the lithium from the resin by contacting it with an aqueous wash liquor. This process has the disadvantage that only a limited amount of the brine can be processed at any one time. The method is therefore time consuming and costly.
U.S. Pat. No. 4,271,131 to Brown et al. discloses a lengthy process for separation of lithium chloride from brines. The process consists of subjecting the brine to a first solar evaporation step to concentrate the brine and precipitate sodium and potassium chlorides, adding slaked lime to the brine during the first evaporation step to precipitate magnesium, subsequently adding slaked lime and calcium chloride to precipitate sulfate as calcium sulfate dihydrate, separating the precipitated calcium sulfate dihydrate from the brine, subjecting the brine to a second solar evaporation to further concentrate lithium chloride and to precipitate magnesium hydroxide, calcium sulfate dihydrate and calcium borate hydrate, heating the concentrated brine to a temperature above 101.degree. C. to remove the remaining water, heating the remaining salts to a temperature above 200.degree. C., cooling the salts, and extracting the lithium chloride with isopropanol. This process also has the disadvantage of being complicated and time-consuming, and therefore inefficient and costly.
U.S. Pat. No. 4,274,834 to Brown et al. also discloses a process for purification of lithium chloride using an isopropanol extraction. The process comprises evaporating the lithium chloride-containing solution which also contains sodium, potassium, calcium, boron, sulfate and/or organic compounds as impurities, heating the recovered salts to a temperature in the range of 270.degree.-325.degree. C., cooling the lithium chloride to ambient temperature, extracting the lithium chloride with isopropanol, and recovering the solid lithium chloride product. This method has the disadvantage that the salt mixture must be heated to very high temperatures.
U.S. Pat. No. 4,307,066 to Davidson teaches a process for extraction of lithium or calcium from a mixture of metal oxides and silicates by reacting the mixture with a chlorinating agent comprising a gaseous H.sub.2 O-HCl mixture at a temperature of 300.degree.-1200.degree. C. and subsequently water leaching the metal chlorides from the resulting mixture. This method has the disadvantage that the salt mixture must be heated to a very high temperature.
While these prior art methods successfully separate lithium chloride from alkali metal chlorides, they do not separate lithium chloride from calcium chloride. Lithium chloride and calcium chloride have a very similar solubility rate, particularly in alcohol. It is therefore difficult to dissolve one while leaving the other undissolved.
Application of this invention to recovering lithium chloride from a geothermal brine is fully described in the U.S. Department of the Interior-Bureau of Mines Report of Investigations 8883, Recovering Lithium Chloride From a Geothermal Brine, by L. E. Schultze and D. J. Bauer, 1984.